mb1058 said:
Jrfuda,
Maybe I misunderstood your setup but the fans should be faced so that they blow out of the rack. In other words, they should be pulling the warm out through the fans. That may explain why you are getting higher number than you would expect.
There are three ways to look at using fans to cool cabinet.
1.) As you suggested, you can use fans to force air out of the cabinet. This is a good technique, however, the air you remove has to make its way back into the cabinet somehow, this is usually by any other openings in your cabinet - gaps under door, cracks & crevices, or openings in the back where you make your connections.
2.) The method I use, you can use fans to force air INTO the cabinet. In this case, air is forced OUT of the same gaps, caracks, crevices, and openings that air is sucked into using the alternative method. I prefer this method, becuase, when you use it in conjuction with filters over your fans, you force relatively dust-free air into your cabinet, keeping your components cleaner. Using the other method, dusty air gets sucked into thr cracks and crevices. Ever notice how a PC case always has dust built-up by places like the CD/DVD Drive and connection openings? That's becuase air is being sucked into those areas.
3.) Use a combination of air forced into and air sucked out of the cabinet. This is porbably the best method if done properly. The goal is to move slightly more air into the cabinet then you are forcing out of the cabinet, creating a positive pressure enviroment in the cabinet. This creates great airflow, and still maintains the dust control due to the positive pressure. A lot of newer PC cases have this feature, usually two fans blowing air in, and one (usually in the power supply) blowing it out. This allows both positive pressue and control of how the air flows accross the components. the only reason I do not use this on my equipment rack is becuase the back is wide open, and does not facilitate this.
My equipment rack consists of two sections - left and right. Each section has two 12V fans forcing air into it. The sides are "joined" by several 3" holes in the panel between them, allowing for some air to pass between the sides, though most air is forced out of the back of the cabinet. However, I do notice a very slight exhasut of air around the gaps around the glass front doors of the two sides.
Also, given the orientation of the 622's fan, using an exhaust fan where it is mounted would work counter to i the 622's intake fan. Currently, one of the two fans mounted on the 622's side of the cabinet blows directly into the 622's fan intake - and the additional air from it, and the second fan blow accross the top and bottom of the 622. This also shows that the designers of the 622 decided to use a fan blowing air into the 622 rather than a fan blowing air out of the 622.
As a side note - a fella over at DBS talk bought an inexpensive USB-powered PC fan and is using it - quite successfully - to augment the cooling of his 622. I think he just has it blowing across the top of his 622.